Spent a good deal of time doing some good old fashion PvP in Warburg, here's what I noticed.
Let me note, I played in the arena once in WoW, and several fights when the arena was first added to CoH. Then I played in the CoV beta player vs villain fights. That is the extent on my PvP experience. I am by no means an expert and I still have a lot to learn.
First, almost all the PvPing was occuring right outside the safe zone. This is not to just pick off solo players or noobs not knowing better. There are many reasons why this is a good place to stage your fight. First, it is the shortest distance to the hospital, so when someone or yourself dies from your team, you can get right back in the action. Second, when multiple teams are really upset because not only are you holding them, but you keep healing your teammates, and they start coming at you with a vengance anytime you're near, it helps to have a safe place to retreat nearby.
When talking to the contacts there, one of them very clearly states in red that while the missions are not PvP, they are in a PvP zone, so you will most likely encounter PvP and if you don't want to, don't accept the mission.
As far as PvPers blocking the way of those that want to explore or do missions there, that's like saying the rebels couldn't get off Hoth (or that for some strange reason they had to fly past that one part of space where the empire was). I mean, its a big map. There's a lot of ways to go around.
Not once while in the fights was I able to tell if someone was on a team or not. There were times when I thought I had figured it out (actually, there was a FF and tank that travelled together), where a few people would be beating on me, and I figured they were teamed, but then as my body was flattened, they would turn on each other. There were times where I thought someone was solo (because they were by themselves), so I figured, I'm a weak controller (meaning I'm not slotted for damage in the least bit and had 1 power total that did any damage, and even with the double dmg while held, i couldn't kill a blaster before he came out of the holds), I'll give it a shot. Then a minute into the dual, their entire teams pounces on comes out of nowhere and pounces on me (or at least I think it was his team). This happened a lot.
My tank has been horribly gimped since I last played her (long ago). I started to use her in PvP, but after seeing how weak she was, took her to missions, then realized she was weak all around. I know there's been some gimping all around, but there were some really strong tanks while PvPing. In fact, most of the players seemed to be tanks and scrappers. Next were blasters, but they seemed to either stay in the air, hidden, or zooming around with SS (which I adopted as my method of defense). There was a handful of defenders. Some Rad ones were standing their ground well. FF ones were upsetting the tanks and scrappers, especially with the bubble that pushes people around. Then I think I saw maybe 2 other controllers out there. Over the course of 3 hours or so.
I thought it was fun once I had teamed up. At first I thought it'd be really mean and tough. Then I teamed with a small group, who, after taking out a defender trying to snipe us, invited him to our team. Then I realized that its all just fun. It happened again later where a group a partner and I were fighting (2 on 4 and we were holding our own), invited us to their team. As long as there is that kind of respect going on, and that its not too rare, I'll keep playing PvP.
BTW, he seemed to be a pretty decent player, but his build also seemed pretty tough. Ice Blaster. Watch out for them ;)